The present invention relates to belt drive systems and, particularly to a belt tensioning device for use in a belt drive system. More particularly, the present invention relates to a pivoting belt tensioning device for use in a variable speed drive of the type used in self-propelled lawn mowers.
Belts are often used to transmit power between motors and driven machinery. V-belts are used in many household, automotive and industrial applications as a power transmission element. For example, a belt can be used to transmit power from a motor to a drive mechanism of a light duty self-propelled lawn mower. Typically, a power transmission belt is wrapped around a driver pulley and a driven pulley.
Belt mediated transfer of engine power to drive mechanisms typically requires an apparatus for maintaining tension on the belts. Traditionally, belts are prevented from dislocation or slippage from a belt sheave by belt idler pulleys. In such conventional devices, an idler pulley may be positioned to contact a rotating belt. The idler pulley is spring loaded traverse to the rotating belt to increase the tension on the belt and prevent the belt from slipping or being thrown off a belt wheel. Unfortunately, this type of traditional idler pulley system is permanently mounted relative to the belt, and its location cannot be varied to allow for speed adjustment.
According to the present invention, a pivoting belt tensioning device includes a pivoting bracket, a slide member connected to the bracket to slide between retracted and projected positions, and a variable speed drive pulley mounted on the slide member to move therewith. The drive pulley is configured to receive a power transmission belt coupled to a drive motor and a drive belt coupled to a driven pulley or the like.
In preferred embodiments, a spring is coupled to the pivoting bracket and the slide member to maintain a proper tension on the two belts coupled to the variable speed drive pulley. The pivoting belt tensioning device is pivotable about the pivot point established by the pivoting bracket between a normal "low speed" position wherein the slide member is projected away from the pivoting bracket and various "high speed" positions where the slide member is retracted toward the pivoting bracket. A bowden wire and mechanism (or the like) attached to the slide member is used to pivot the tensioning device to a high speed position by causing the slide member to move relative to the pivoting bracket toward a retracted position as the bracket pivots. During such sliding and pivoting movement, the spring acts to maintain proper tension on both belts coupled to the variable speed drive pulley mounted on the slide member. The power transmission belt acts normally to move the slide member to its projected position and pivot the tensioning device to its normal low speed position.
The present invention provides a belt tensioning assembly that both tensions a belt and allows easy adjustment of belt sheave distance. The belt tensioning assembly is mounted on a base such as a deck of a light duty self-propelled lawn mower. The assembly includes a bracket pivotably attached to the base and a belt sheave such as a variable speed drive pulley for holding a pair of rotatable belts. Typically, one of the pair of rotatable belts is a power transmission belt that is connected between a drive pulley of a power source (such as an internal combustion engine) and the belt sheave. The other belt is a drive belt that is connected between the belt sheave and a driven pulley included in a drive box for driving wheels of a lawn mower.
A slide bracket is slidably attached to the pivotable bracket and the belt sheave is attached to the slide bracket. Movement of the slide bracket relative to the pivotable bracket is regulated in part, by a spring biasably attached between the slide bracket and the pivotable bracket. The slide bracket is retained in sliding relationship to the bracket by retaining means that includes a ledge positioned in spaced apart parallel relationship to a retainer. The ledge and the retainer define therebetween a slide channel dimensioned to accommodate the slide bracket for sliding movement relative to the pivotable bracket. Optionally, to reduce manufacturing costs, the ledge and the retainer are formed from an integral piece of sheet metal folded to define the slide channel.
An aperture is formed in the pivotable bracket to allow pivotal mounting of the pivotable bracket relative to the base. A pivot mounting stud dimensioned to extend through the aperture is formed to include a head dimensioned to engage the pivotable bracket. A cylindrical shaft is attached to the head and dimensioned to pass through the aperture to allow pivotal motion of the pivotable bracket relative to the base. The pivot mounting stud is formed to include a threaded shaft that extends through an aperture in the base and is attachable to the base with a nut.
The belt sheave is a variable speed drive pulley that includes a center wheel mounted for movement between a pair of side wheels to define a first and second beltways respectively between the movable center wheel and each of the pair of side wheels. The movable center wheel is mounted to rotate on a shaft fixedly attached between first and second slide bracket arms mounted on the slide bracket. Limited longitudinal movement along the shaft is allowed in response to pivotal movement of the bracket.
In preferred embodiments, the component parts of the belt tension assembly are configured to interlock into an operational form without requiring fasteners, welds, glues, or other attachment devices. Replacing belts is quick and simple, only requiring an operator to extend the shelf bracket arm until the bracket arms slip out of the slide channel. Each component is inexpensively constructed from one stamped or formed piece of metal, and only a single pivot bolt is required to attach the assembly to a deck of a lawn mower. Advantageously, the entire tensioning device is compact and easy to service.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as present perceived.